The effect of radiation on tensile properties, notch bend properties, and fracture toughness was determined on A212B steel from the Pathfinder reactor surveillance program and on A533B steel from the U.S. AEC Heavy Section Technology program. Impact tests were performed on an instrumented Charpy machine which provided load-deflection data in addition to energy absorption data. Valid fracture toughness values were obtained from precracked Charpy specimens.

The results of the notch bend tests on the irradiated steels indicated that the radiation induced increase in the ductile-brittle transition temperature was mainly due to the large radiation induced increase in the friction stress. Radiation reduced the strain rate sensitivity of the yield stress but did not change the temperature dependence of the yield stress. The microscopic cleavage strength was essentially unaffected by irradiation. The relationships between the metallurgical fracture parameters (Cottrell-Petch) and the ductile-brittle transition temperature (DBTT) and fracture toughness (KIc) were established. These relationships were used to predict the radiation induced change in fracture toughness (both DBTT and (KIc) from a knowledge of the effect of radiation on metallurgical fracture parameters.